BTO migration blog

Spring and autumn are exciting times for anyone who watches birds. Here on this blog we will make predictions about when to expect migrant arrivals and departures, so that you know when and where to see these well-travelled birds.

Friday, 28 April 2017

The nature of migration generally this spring
has been one of sudden flurries followed by slow trickles. This week continued
along much the same lines: a glorious weekend with a southerly airflow and wide
isobars saw the floodgates open for northbound migrants to stream into the
country. Coastal localities were inundated with Willow Warblers, Blackcaps and
Wheatears, and species like Redstart, Sedge Warbler, Whitethroat, Ring Ouzel
and Grasshopper Warbler took advantage of the passing weather front to move in
from the continent. Then the traffic lights turned red: a complete flip in the airflow
saw bitter northerly winds dominating for much of the week; temperatures
plummeted into the single figures and flurries of snow and hail across the
north of the UK further added to the week’s wintry feel.

Willow Warbler by Ben Porter

The calm conditions over the weekend made
for some great arrivals here on Bardsey: bushes were brimming with Willow Warblers
and Blackcaps; Grasshopper Warblers sent out reeling songs from the damper
wetlands; Swallows and Sand Martins zipped northward overhead; and seemingly
every grassy knoll and bank was topped with a Wheatear! Greenland-race
Wheatears have been one of the dominating migrants on the island this week,
their larger size and deeper orange belly contrasting with a flash of white as
they alight with hard ‘chacking’
calls. An excellent arrival saw over 250 birds on the 20th, although the
national reporting rate on Birdtrack still shows below-average occurrence. It
looks like the pressure front next week is going to help these leucorhoa birds make their long-distance
flights to the Arctic tundra via Iceland and Greenland.

Wheatears by Ben Porter

Cuckoos and Turtle Doves have yet to make
it over the Irish Sea to the island, although both species reached Scotland
this week, with a Turtle Dove on the isle of Rhum and a Cuckoo in Lothian!
Three of the BTO’s satellite-tagged Cuckoos are now north of the Pyrenees and
should make the home stretch to join ‘Selborne’ with a brisk south-east
tailwind in the next week. Keep up to date with their movements here

A smattering of colourful scarcities
arrived in the UK this week, including Golden Oriole, multiple Hoopoes, at
least three Bee-Eaters (one of which even paid London a visit!), White-spotted
Bluethroats, Serin, Red-footed Falcons and the spring’s first Savi’s Warbler.
We can expect to see plenty more of these overshooting continentals as we enter
May, plus some non-passerine visitors such as Temminck’s Stints on inland
reservoirs. Conversely, Waxwing numbers are likely to dwindle as birds continue
to dissipate north-east – we still had around 600 birds in the country last
week, although they were absent from Ireland, Wales and the South-west.

Whimbrels should arrive in earnest over the
next ten days as we approach their peak spring reporting period. The numbers
here on Bardsey Island are still below-average for the time of year. Contrast
that to the national picture, and the reporting rate is slightly above the historical
average, fast-approaching 7.5% of Birdtrack user’s lists. Keep an eye out for
colour-ringed birds amongst migrating flocks: they are most likely to be from
Iceland, but a few sites in the UK also carry out colour-ringing on these
waders, including Bardsey Bird Observatory.
Make sure you report colour-ring sightings and email the Iceland project (icelandwader@gmail.com)
should you see any. It’s through anaylsis of ringing recoveries and recent
satellite tracking that has revealed some impressive autumn
movements of Icelandic Whimbrels from Iceland to North Africa. It’s also
indicated that most birds on the east coast – both in spring and autumn – are
likely to be Scandinavian.

Whimbrel ring recoveries from BTO. Whimbrel images by Ben Porter

Early May is one of the best times of year
to catch up with trips of Dotterels as they touch down on hill tops and coastal
spots en route to their breeding
grounds. A scattering of birds have already been seen over the last week,
including at favoured sites such as the Great Orme in North Wales. Lancashire’s
Pendle Hill will no doubt host a few of these superb waders in the next few days.

So what of the week to come? A low-pressure
system rolling in from the Atlantic over Saturday and Sunday will see the
strong winds switching around to the south-east, which could provide the
encouragement needed for migrants to move up through France and continue
northwards in the UK. A widening of isobars and an area of high pressure over
France and Iberia in the earlier part of the week should make for a good
arrival of more warblers, chats and waders. Temperatures should climb a little
higher too, which will hopefully encourage the invertebrate life to emerge and
provide weary migrants with much-needed refueling!

Low pressure is due to arrive on Saturday - image from Met Office.

We’ve almost welcomed back the full
complement of spring migrants as far as songbirds are concerned, although Spotted Flycatchers have yet to appear, and the peak arrivals of Wood Warblers,
Pied Flycatchers, Yellow Wagtails, Garden Warblers and Lesser Whitethroats will
probably occur over the next week or two given the promising outlook.

Spotted Flycatcher by Ben Porter

If you’re heading out over the weekend,
listen out for the liquid gold song of the Nightingale – birds should be back
on breeding territories very soon. The bright sunny weather forecast for early
next week will be perfect for Common Swifts to scythe their way overhead in
screaming flocks. If you haven’t already, why not consider fitting a Swift
nestbox to your house? There is just enough time before they return! There are
plenty of tips at www.swift-conservation.org.

The reporting rate for Common Tern and Arctic
Tern is on the increase, and the strong winds this weekend might make
seawatching a productive option to spot flocks passing by. You might also be in
with a chance of seeing Pomarine, Arctic and Great Skuas passing the coast.
Rarities in the coming week could take the form of more overshooting
continental migrants such as Black-Winged Stilts and Golden Orioles, although
the south-easterly wind might favour perhaps a Collared Flycatcher, Citrine
Wagtail or Red-throated Pipit even on the east coast.

Friday, 21 April 2017

The stop-start nature of this spring's migration has continued over the past week but breaks in the weather fronts allowed through a nice flurry of Ring Ouzels with over 60 records yesterday alone. Over the past week Ring Ouzels have been reported from the Isle of Wight to Edinburgh with 17 at Burnham Overy in Norfolk on the 20th April and 27 in the Cot Valley in Cornwall on the 18th April. Wheatears also arrived in good numbers and the graph below from BirdTrack shows that after a lag earlier on, the percentage of BirdTrack users seeing Wheatear has now caught up with the average for this time of year.

This is the best time of year to look out for Red-rumped Swallow and right on cue there have been half a dozen or so sightings over the past week. If you're visiting any coastal locations or freshwater marshes over the coming week look out for Swallows with very pale (sometimes reddish) rumps!

With high pressure dominating through well into next week we can expect a good arrival of migrants. We should see Pied Flycatcher, Whimbrel, Yellow Wagtail, Hobby and Arctic Tern all arriving in good numbers and more of our Turtle Doves returning too. We are receiving more reports now of House Martins returning to their nest sites, if you have any breeding near you then we need your help with our House Martin nest survey.

Three of our satellite-tagged Cuckoos are back in Europe now with one already back at his breeding grounds in the UK. Over the next two to three weeks we'll be heading rapidly towards the peak for Cuckoo records so if you want to hear a Cuckoo this year, this is the time to get out and listen. If you're very lucky you may even encounter an early Bee-eater, Squacco Heron or Purple Heron and it is worth looking out for rarer waders like Pectoral Sandpiper and Marsh Sandpiper stopping off on passage.

Cuckoo by Robin Lee

Over the course of the weekend, a cold weather front moving from north to south through Britain could produce a decent 'fall' of grounded migrants. Saturday morning looks like your best bet to head to a coastal watch point to witness this phenomenon for yourself, especially if there is a little rain early on . There is the potential for much colder weather early next week, with snow over much of Scotland and down to central England. How will our recently arrived migrants (and early breeders) cope with this cold snap?

Thursday, 13 April 2017

The stop, start nature of this spring migration continues. The quiet spells in the weather provide windows of opportunity for migrants heading north through France and Spain, only for them to be closed by the next front to move through. This Friday and Saturday are a good example.During the night of Thursday into Friday the conditions in France and across the Channel look good for birds wanting to make a move (see chart below).

However, fast-forward to the same period on Friday going into Saturday and a front in the channel will have a blocking effect on birds heading north over the channel.

Of course it will depend on the actual timing of the front moving through. If it is a little late, birds could set off across the channel and be grounded on the south coast as they encounter the front. If it moves earlier than forecast birds might be grounded in northern France, unable to move until the front has passed.So, what does this mean for the weekend?As the spring progresses more and more birds will take advantage of any window in the weather. We should see pulses of arrivals that by now should include Swallows in particular as they do still seem thin on the ground. Yellow Wagtail, Tree Pipit and Redstart should also be a feature, along with Ring Ouzel, Cuckoo and House Martin.A few Garden Warbler should join the Blackcaps, although it feels like there are still a lot of Blackcap to arrive too. Reed Warblers should also take advantage of quiet overnight weather and make it back to their reedbed territories.Where are all the Wheatears? It is a little worrying that Wheatear is trailing well behind its historic average in BirdTrack. The purple arrow on the graph is where it should be, whilst the blue dots are where we are this spring. Hopefully, they are just held-up and will flood in as soon as conditions allow, but you have to wonder what sort of winter they have had.

BirdTrack reporting rate for Wheatear

On the rarity front, the warm southerly airflow we saw last weekend did bring a few overshoots with it in the shape of two or three Purple Herons, a Little Bittern, a couple of Western Subalpine Warblers, a Night Heron, a couple of Red-rumped Swallows and Woodchat Shrikes, two or three Black Kites and at least one Hoopoe. However, pride of place must go to the splendid male Rock Thrush that was found on St Martins, Isles of Scilly.

Friday, 7 April 2017

During the last few weeks migration has been somewhat
stuttering. Breaks between weather fronts crossing Europe allowed birds to move
only for them to be stopped by the next batch of fronts to move through. That might be
about to change this weekend as high-pressure moves over the UK. The winds will
turn southerly, and at least for a short while will come from as far south as North
Africa. This should open the floodgates for birds such as Swallow, Blackcap and Willow
Warblers, birds that should be fairly widespread at this time of the season
but are still a little thin on the ground.

Hobby by Jason Thorpe

We are still a week or so away from the peak migration
period but we should see lots of birds arriving in the next few days. Hobby,
Grasshopper Warbler, House Martin, and Sedge
Warbler could arrive in force, along
with the first flood of Whitethroat and,
as the winds turn more south-easterly around mid-week, a few Lesser Whitethroat too.

Redstart should
be seen more widely, and Pied
Flycatchers are worth looking out for too.
In fact with the conditions looking so good, most of our summer migrants
should be represented over the next few days, perhaps with the exception of
those that have a late spring arrival time, such as Swift, Spotted Flycatcher and Quail.

Cuckoo by Charles Tyler

Six out of our seven satellite tagged Cuckoos are still south of the Sahara in West Africa but we do
have one that has crossed the desert. Hampshire Cuckoo "Selborne", has been in northern Spain for around a week and will probably make the
final leg of his journey home in the next week. Although none of our tagged
Cuckoos have made it as far north as the UK, Cuckoo is definitely worth
listening out for in the next few days and keep an eye on the Cuckoo tracking maps for daily updates on the position of our tagged birds.

At sea, Common Terns
on the move could be joined by the first Arctic
Terns of the spring, and when terns are on the move skuas move too, so
there ought to be a few Arctic and Great
Skuas seen.

Arctic Skua by Moss Taylor

Conditions look to be perfect from the early hours of Friday
morning right through to at least the early part of next week, and whilst the
south coast ought to be the place to be, we could all enjoy spring arrivals
during this time.

Black Kite by Jill Pakenham

With the warm winds coming from so far south, overshooting
spring migrants should also be a feature. Along with the possibility of a few
more of the birds we have seen during the last week, Red-rumped Swallow, Black-winged Stilt and Woodchat Shrike. With the forecast weather it looks like we could
be in for an arrival of southern herons,
Purple Heron, Little Bittern and
Night Heron are all on the cards. We could also see the odd Black Kite and maybe Sardinian Warbler.

The conditions are also good for departing migrants and it
is worth keeping an eye out for the last Redwings
and Fieldfares, and at sea, Brent Geese.